Hydrofluorocarbon (HFC) products are widely utilized in many applications, including refrigeration, air conditioning, foam expansion, and as propellants for aerosol products including medical aerosol devices. Although HFC's have proven to be more climate friendly than the chlorofluorocarbon and hydrochlorofluorocarbon products that they replaced, it has now been discovered that they exhibit an appreciable global warming potential (GWP).
The search for more acceptable alternatives to current fluorocarbon products has led to the emergence of hydrofluoro-olefin (HFO) products. Relative to their predecessors, HFOs are expected to exert less impact on the atmosphere in the form of a lesser, or no, detrimental impact on the ozone layer and their much lower GWP as compared to HFC's. Advantageously, HFO's also exhibit low flammability and low toxicity.
As the environmental, and thus, economic importance of HFO's has developed, so has the demand for precursors utilized in their production. Many desirable HFO compounds, e.g., such as 2,3,3,3-tetrafluoroprop-1-ene or 1,3,3,3-tetrafluoroprop-1-ene, may typically be produced utilizing feedstocks of chlorocarbons, and in particular, chlorinated propenes, which may also find use as feedstocks for the manufacture of polyurethane blowing agents, biocides and polymers.
Unfortunately, many chlorinated propenes may have limited commercial availability, and/or may only be available at prohibitively high cost, due at least in part to the complicated, multi-step processes typically utilized in their manufacture. For example, in methods that utilize allyl chloride or 1,2,3-trichloropropane as starting materials, successive dehydrochlorinations and chlorinations with elemental chlorine may be done until the desired number of chlorine atoms has been added. Or, some conventional methods call for the chlorination of chlorinated alkanes having fewer chlorine atoms than desired in the final product.
At some point in many, if not all, such processes, mixtures of isomers of tetrachloropropanes and pentachloropropanes may typically be produced, that once produced, may either be difficult to remove and/or react to produce undesirable by products. And so, many conventional processes call for the removal of these isomers, thereby lowering the yield of such processes. And, doing so introduces additional cost and time to an already multi-step and typically expensive process. Additionally, such processes may also result in the production of large amounts of contaminated waste water having high quantities of sodium chloride, and one or more chlorinated organic(s). The waste water thus must typically be treated before releasing it to the environment, requiring even further expenditure. Any recovered sodium chloride provides little in the way of recoverable cost.
It would thus be desirable to provide improved processes for the production of chlorocarbon precursors useful as feedstocks in the synthesis of refrigerants and other commercial products. More particularly, such processes would provide an improvement over the current state of the art if they were capable of minimizing, or even eliminating, the production of the less desirable tetrachloropropanes and pentachloropropanes, and/or economically utilizing any amounts of the less desirable isomers that may be produced. Further benefit would be realized if the processes would provide by-products of higher commercial or reuse value than sodium chloride.